Typical fluid process control systems comprise various components for controlling various process parameters. For example, a fluid process control system may include a plurality of valves for controlling volumetric flow rate, temperature, and/or pressure of a medium flowing through the system. The end product is often dependent on the accuracy of the control of these parameters, which is, in turn, dependent on the geometry and characteristics of the control valves. For example, control valves are specifically designed and selected to provide for particular flow capacities and pressure changes. If and when these characteristics are compromised, the quality of the end product may be affected.
In many process control systems, the character of the control valves may be compromised by the particular media flowing through the system. For example, the media may include a fluid contaminated with or inherently containing particulate matter that can impact the internal surfaces of the control valve. After prolonged use, the particulate matter can begin to erode the control valve. Additionally, as mentioned above, control valves are often implemented to generate a pressure change in the process media. In many circumstances, the control valves are designed to generate pressure drops below the vapor pressure of the media, thereby rapidly increasing the velocity and volume of the media due to a phase change of the process media. Such rapid increases are often referred to as flashing, which can damage the control valve. Flashing is another example of a potentially erosive situation. Further yet, another problem with fluid process control systems includes the potential for crystallization of the media due to changes in pressure and temperature. Further still, in various fluid process control systems, the media may include components that may electrically or chemically react with the control valve to cause corrosion. Thus, it is well-known that erosion and/or corrosion can affect the useful life of any given fluid process control system component.
To counteract the detrimental effects of erosion and/or corrosion it is generally known to provide a sacrificial element within at least a portion of the interior of the control valve. This sacrificial element, such as a liner made from Stellite® available from Deloro Stellite Company Inc. of Goshen, Ind. or a ceramic liner, therefore takes the brunt of any impact of particulate matter, as well as the effects of flashing. For example, a typical control valve includes a valve body defining an inlet, an outlet, and a flow path disposed between the inlet and outlet. Often, the control valve receives a high pressure, low velocity medium at the inlet. Upon passing through the control valve to the outlet, however, the state of the medium changes to low pressure, high velocity and, in some circumstances, from a liquid to a gas, as mentioned above. Therefore, debris or particulate matter in the medium tends to have more of a detrimental impact on the outlet of the valve body because of the higher velocity and lower pressure. Thus, protective sacrificial liners are oftentimes provided to line the outlet portion of the valve body.
Typical sacrificial liners comprise thin walls secured to the inner surface of the outlet of the valve body. In one conventional manufacturing process, the sacrificial liner is first heat shrunk into an inner sleeve. The sleeve and liner assembly is then secured into the outlet of the valve body. In another conventional manufacturing process, the sacrificial liner is first press-fit into an inner sleeve prior to securing the assembly into the outlet of the valve body. In either of these manufacturing processes, the liner and the sleeve must be prefabricated within relatively small tolerances. Once assembled, the sleeve and liner assembly is generally removable from the valve body; however the heat shrunk or press-fit liner is essentially permanently attached to the sleeve to such extent that it is un-repairable and non-replaceable. Thus, when the liner erodes, corrodes, or otherwise becomes damaged, the entire sleeve and liner assembly must be replaced.